As a collector and not an "investor" I don't GAF about the "value". Frankly they're never near accurate enough anyway. I'd personally focus on accuracy of information, availability of variants where possible to choose from (i.e. "I have X variant"), and just overall robustness and searchability of the data. Not me, but someone out there wants to be able to filter to "All Black Box Mario NES variants" and someone ELSE wants to filter to "All Adventure Island games across all systems".
I'd focus on the "collecting" aspect of it, personally.